The well known phenomenon of streaming potential is typically used to measure surface potential or charge of a material in an electrolyte. Measurements of capillary flow and on dispersions of finely divided particles may be used to determine surface charge. Measurement techniques generally employ a specialist instrument dedicated solely to such measurements. Measurements using capillary flow or dispersed particles may require that the sample material be in a particular format that may not always be convenient or straightforward to prepare.
U.S. Pat. No. 7,217,350 discloses a method of automatically determining an electric charge-related characteristic or derived parameter of particles in a dispersion or of a cell wall, in which a dispersion is illuminated with light from a light source and light scattered by particles in a detection volume is detected. In one arrangement the detection volume comprises a transparent capillary cell with a pair of electrodes at opposing ends, forming a closed volume for a dispersion of particles in a liquid. In another arrangement a pair of electrodes is provided on opposing side walls of a cuvette that is partly filled with a liquid sample.
U.S. Pat. No. 7,449,097 discloses an electrophoretic mobility measuring apparatus comprising a cell for confining a sample, the cell having a transparent electrode side wall and another electrode on an opposing cell wall. A voltage is applied across the electrodes and light is incident upon the inside of the cell through the transparent electrode. Scattered light is received through the transparent electrode and a Doppler displacement is measured.
US 2011/0210002 discloses a method and apparatus for measurement of electrophoretic mobility of particles and molecules in solution, in which a sample of particles is placed in a cell containing two electrodes across which is applied an alternating electric field. A monochromatic light beam passes through the sample and light scattered by particles is collected and collimated as it exits the cell. Optical phase information is used to measure particle movement.
EP 2423671 discloses a particle characterization cell and instrument, in which a tubular cell main body forms an internal space with a pair of electrodes arranged to face each other in the internal space, laser light irradiating a liquid sample in the internal space being scattered by particles in the liquid sample and detected by a light detecting part.
Each of the above mentioned documents disclose measurement of electrophoretic mobility of samples in the form of finely divided particles suspended in an electrolyte liquid.